|By Kylie MacLellan and William James

|By Kylie MacLellan and William James

|By Kylie MacLellan and William James

LONDON (Reuters) - British Prime Minister Theresa May cleared the final hurdle standing between her and the start of Brexit negotiations on Monday after parliament passed legislation giving her the power to start the EU exit process.

Members of the lower house of parliament voted to throw out changes to the bill made by the upper house earlier this month, after the government argued it needed freedom to operate without restriction to get a good deal.

Despite an attempt by the Liberal Democrats in the unelected upper chamber, the House of Lords, to re-introduce the conditions, the Lords also went on to approve the legislation unamended late on Monday.

"We are now on the threshold of the most important negotiation for our country in a generation," Brexit minister David Davis said in a statement.

"So we will trigger Article 50 by the end of this month as planned and deliver an outcome that works in the interests of the whole of the UK."

The bill will now be sent to the queen for symbolic approval which could be granted as early as Tuesday morning, leaving May ready to start a two-year negotiation period, as set out in Article 50 of the EU's Lisbon Treaty.

May's spokesman hinted on Tuesday, however, that she might do so closer to the end of the month.

Her task in negotiating Britain's EU exit was complicated on Monday by Scottish First Minister Nicola Sturgeon demanding a new independence referendum, to be held in late 2018 or early 2019, once the Brexit terms are clearer.

In recent weeks, the government had lost two key votes in the House of Lords which added conditions to the bill to demand that May guarantee the rights of EU nationals living in Britain and give lawmakers more powers to reject the final terms she reaches with the EU.

But May succeeded in warding off a potential rebellion from a handful of pro-EU Conservatives in the lower chamber, the House of Commons, where May only has a slim majority.

The Commons voted by 335 to 287 to reject the condition on EU nationals' rights, and by 331 to 286 to reject the condition giving parliament a greater say on the final deal.

Earlier May's spokesman said parliament would be involved in the Brexit process.

"We are determined parliament will be engaged all the way through the process and afterwards," he told reporters.